This application claims the priority of Application No. 102 005613, filed Jan. 19, 2002, in Germany, the disclosure of which is expressly incorporated by reference herein.
The invention concerns a phase controlled antenna subsystem with a passive antenna array which is especially applicable to a radar system, an SAR, for antennas in systems for electronic warfare or deployment guidance, as well as for navigation and communication systems. Possible platforms for the integration of the functions according to the invention are ground, naval systems, airplanes, satellites, drones and guided missiles, as well as buildings or vehicle bound-systems.
A radar system with phase controlled antenna array is known from U.S. Pat. No. 5,940,031 which contains a data and supply network and a number of installed and interchangeable transmit/receive modules containing a transmitter and receiver circuit and a number of antenna elements coupled via circulator circuits with the transmitter and receiver circuits. With the known radar system, the transmit/receive module is installed at the rear side of the data and supply network, which is constructed in several layers containing a cooling element structure, an power supply structure and a high frequency supply structure. From the transmit/receive modules that had been installed on the backside of the data and supply network, high frequency connection elements are installed on the respective antenna element at the front-side of the data and supply network and connected to the coupled circulator circuit in each case. The transmit/receive modules are interchangeable from the backside of the data and supply network, so that the radar system must be accessible from the rear side for maintenance.
Published highly miniaturized transmit/receive modules are manufactured without internal circulators and internal radiating elements. Therefore, their RF performance suffers on a high amount of RF losses and electrical and mechanical interfaces.
One difficulty exists in many application areas of radar and ECM systems (ECM=Electronic Counter Measures) with active phase controlled antenna arrays, e.g., for airplanes: There is very little space available for the accommodation of the radar system, and access from the rear is often impossible or only possible under difficult circumstances.
It is an objective of the present invention to provide a radar system of the above-mentioned type that requires little volume whereas the transmit/receive modules are easily interchangeable for maintenance and repair work.
A radar system with a phase controlled antenna array according to the present invention includes a data and supply network and a number of transmit/receive modules arranged interchangeably on the data and supply module containing in each case, transmitter and receiver circuits, a plurality of circulator circuits and a plurality of antenna elements coupled via the circulator circuits with the transmitter and receiver circuits. According to the invention, the transmitter and receiver circuit, related control electronic, circulator circuit and antenna element are combined in each transmit/receive module, and the transmit/receive module is arranged interchangeably on the irradiation side or at the front side of the radar system.
An essential advantage of the radar system of the invention is that an exchange of the transmit/receive module can take place from the irradiation side or front side of the radar system, which is very advantageous for many applications. It is another advantage of the radar system of the present invention that the antenna array can be adjusted to a curved surface when a structure-integrated antenna or conformal antenna is desired. Another advantage of the radar system of the present invention are the reduced number of RF interfaces and use of short high frequency lines to the antenna and therefore a low noise figure, lower high frequency losses and a low signal coupling. Finally, it is an advantage of the radar system of the present invention that a simple construction of the data and supply network is possible.
By use of modified transmit/receive modules (without amplifiers for transmit and receive functions) passive phased antenna arrays can be realized also.
According to an advantageous embodiment of the invention, the transmitter and receiver circuit, the circulator circuit, and the antenna element are integrated in the form of a multi-layered structure into the transmit/receive module.
Preferably, the antenna element is installed in the form of a planar antenna at the upper side of the transmit/receive module.
According to another preferred embodiment of the invention, the multi-layered construction contains several substrates arranged one on top of the other that carry the components of the transmitter and receiver circuits and the circulator circuit.
According to another advantageous embodiment, a first substrate is arranged on the side of the transmit/receive module facing the data and supply network which carries a high frequency power amplifier of the transmitter and receiver circuit to improve heat removal.
According to yet another advantageous embodiment, a second substrate is installed on the side of the transmit/receive module facing away from the data and supply network, and the circulator circuit carries the antenna element, as well as parts of the transmitter and receiver circuit. This makes possible a reduction of the space requirement, as well as an optimization of the noise level.
According to an advantageous further development of the above-named embodiments, at least one additional substrate is installed between the first substrate and the second substrate that carries additional circuits, especially a high frequency processing part and/or a digital processing part.
According to another advantageous embodiment of the radar system according to the invention, the substrates are constructed in one piece with a frame structure that simultaneously forms a housing of the transmit/receive module and a mechanical connection among the substrates.
Preferably, the data and supply network is a mechanical carrier structure for the transmit/receive module that simultaneously contains a cooling structure for the transmit/receive module.
Preferably, the data and supply network is multi-layered structure that contains a cooling structure in the form of a first layer and at least one more, a high frequency data and power supply network containing a circuit structure in the form of a second layer.
The cooling structure is preferably installed at the transmit/receive module facing the wall of the data and supply network, and the cooling structure is designed as an active cooling structure where cooling fluid flows through. Additionally, it is preferable that the first substrate carrying the high frequency power amplifier of the transmitter and receiver circuit stands in an intensive cooling contact with the thermal structure of the data and supply network.
According to an advantageous embodiment of the invention, the substrates and/or the frame structure has been manufactured of aluminum nitride (AIN). The substrates themselves are built in several layers of aluminum nitride and contain vertical and horizontal electrical contacts. Other substrate materials could also be used, but reduced performance (e.g. loss, thermal resistance) will be possible. Between the layers are electrical conductor lines (horizontal electrical contacts). These conductor lines are connected vertically with one another by a so-called vias (vertical electrical contacts).
According to another preferred embodiment of the invention, the substrates are stacked one above the other and soldered together. The solder connection consists preferably of hard soldering globules that the soldering material flows around. Preferably, the substrates are soldered together at the frame structures.
A metal sleeve that is fastened using solder, welding or gluing technology preferably encloses the sender/receiver module. The sleeve is preferably used to secure an electromagnetic screening of the module and the electrical contacts between the substrates and to seal off the module hermetically.
According to an additional preferred embodiment of the invention, an electrical connection is incorporated between the electrical contacts formed by the substrates within the frame structure.
The transmit/receive modules are preferably identical, and are installed at the irradiation side or the front side of the data and supply network.
Finally, according to an advantageous embodiment of the invention, the transmit/receive module is fastened with screws to the data and supply network at the edge or at the corner areas. A frame to fasten a number of transmit/receive modules (e.g. an arrangement for a subarray) could also be used.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompany drawings.